The audio has never been released in the UK before: Bloomsbury heard about its existence when talking to Monica's niece Mary Danby, who manages her estate (it's been republishing her books through its new ebook arm Bloomsbury Reader, something I've expressed my excitement about before). Monica had recorded the reading for the Samaritans in Cape Cod in 1984 (she'd founded the Samaritans in the US in 1977, having been a Samaritan in London before moving to the US).

"I got goosebumps when I first heard this," says publisher Stephanie Duncan. "It's like listening to Dickens himself reading, since Monica heard it from her grandfather who in turn heard it from Charles Dickens himself." I've had a listen to the beginning, and she's right: hearing Monica intone that classic opening, "Marley was dead: to begin with", is an experience that shouldn't be missed.

Bloomsbury is publishing the audio as part of an enhanced ebook for Christmas, with half of the proceeds going to the Samaritans. It comes with a fabulous interview with Monica – I'd not heard her voice before, and hearing it makes me even more of a fangirl – in which she gives a bit of family history behind the novel's creation.

"He was loaded down with debts," she says of her great-grandfather. "His family were always borrowing from him. His mother and father were always touching him for a loan. His children – not my grandfather I hasten to add – were rather profligate, and he was on his beam ends." So he wrote the book, and ended up publishing himself, making "something like £1,000" and "God knows how many millions of pounds and dollars it has made since".

This is the goosebumps part, though. "All the family sat and Dickens would read the Carol to them when they were children. When we were children, my grandfather sat and read the Carol to all of us. I got the feeling that since he had listened to his father reciting he was giving us a pretty good imitation of Charles Dickens," she says.